is 4.8 watt solar panel enough for charging battery?

[bobg]

I've bought a new 4.8 watt solar panel on e-bay as it seemed cheap and far better than those Mickey Mouse little solar panels that litter e-bay. Am I right in thinking that 4.8 watt will do a battery top-up jobbie with all the usual caveats about daylight hours and sunshine? If not, watch out for it going back on e-bay.

 

[VicS]

I have had a 5 watt panel for a long time. It's permanently mounted and I have found it quite adequate to top up the battery after a weekends sailing with no other serious source of power. I have no major power drains, seldom sail at night but usually have the vhf on and use an Autohelm a fair bit. I try to be economical with cabin lights.

If it failed I would replace it with a similar one.

 

[bobg]

Thanks Vic. Your always sage words could only be improved by my addition of a sprinkling of parsley and thyme. I think we know a song about that, don't we? And of course Simon and Carbunckel nicked that song from Martin Carthy who collected it from somebody long dead. Well, it is Friday night, so we can be a bit silly.

 

[MarkJohnson12345]

My electronics guru told me that my 10 watt solar panel would only produce 10/12's of an amp when pointed directly at the sun.

Rest of the time it might produce from .5 to .2 amp if the wetaher wa good.

Then consider that the battery will probably only absorb 1/2 of the amps put its way, certanly less when the charge rises..

If you are serious about solar panels then you will need a lot bigger one.

But I enjoy watching the charge go in so go with it....

MJ

 

[Superflid]

I've had a 5W job on Tommy for 2 years charging an 85ah battery, engines charge while using the boat, but it's sat for months without use. Bilge pump is only thing connected while it's been left.

I'm just finishing making the deck self-draining, so it'll be easier on the pump now, but for every inch of rain we had previously, it had to pump out approx 50 gallons of water......

Only time I've had a battery problem was due to a stuck float switch.

5W has been fine for me

 

[William_H]

Hi Mark sorry your guru is no guru at all. A ten what panel will only produce a little over 1/2 amp at best.
10 watts is divided by the voltage which is about 18 volts even 20. That is the no load voltage. Not divide by 12 cos it is a 12v system or even divide by 13.75 the actual battery voltage.

Anyway in answer to the post the question is akin to "how long is piece of string?" Your 4.8 watt panel will do a lot better than nothing and only half as good as a 10 watt. But then again your little panel will be easier to mount and less likely to be stomped on.

I use a panel possibly smaller than yours for all electrics (no engine) but then I don't use it in winter and it is Oz summer sun but it keeps the battery up for radio and occasional lights.
don't sell it just add another one if you find it inadequate.
good luck olewill